Spine surgeons have expressed a desire to locate an implant with a low vertical profile instrument to minimize retraction and increase visibility of the implant. Ideally, the instrument and its connection point are sized to be fully contained within the profile of the implant, thus being smaller than the implant and allowing easy positioning or placement of the implant. Additionally, the connection to the instrument should be desirably rigid, with no toggle or rotation in any plane. This rigidity prevents implant movement during the passing of instruments or bone screw insertion.
Conventional inserter instruments possessing chamfer features typically work in one plane, wherein a grabber tip collapses upon the implant in a medial/lateral direction and thereby secures the implant to the instrument. However, even with exacting tolerances, toggle often appears if the user of the conventional instrument were to apply a moment to the posterior edge of the implant (in flexion/extension) in one plane. Conventional inserters with chamfer features also do not take advantage of dissimilar angles at the interface in more than one plane, and so fail to ensure that the anterior surface of the implant bottoms out on the inserter grabber tip.
U.S. Pat. No. 5,443,514 (Steffee) discloses an inserter that grips the side of a spinal implant. See FIGS. 4-6 of Steffee.
US Patent Publication No. 2005-0143749 (Zalenski) discloses an inserter having engagement features forming a vertically-extending dovetail shape. See FIGS. 2A-2C of Zalenski.